1. Technical Field
The present invention relates generally to a probe card for testing circuit, and more particularly to a high-frequency cantilever type probe card.
2. Description of Related Art
Typically, probe cards are widely used in the test of the electrical connection between the electronic devices. Cantilever type probe card is a popular transmission interface between a tester and a device under test (DUT).
The conventional cantilever type probe card includes probes electrically connected to a rigid multilayer printed circuit board. The probes contact pads of the DUT with tips thereof, and the multilayer printed circuit board is electrically connected to terminals of the tester. The printed circuit board is provided with vias for the connection of the circuits on different layers. However, there will be a via stub effect occurred in the vias. Via stub effect is an inductance generated in the vias while high-frequency signals are transmitted through the printed circuit board, and the inductance is high while the frequency of the signals is high. The inductance in the vias provides the high-frequency signals a resistance, which makes the test imprecise.
On the other hand, the conventional tester can't provide the testing signals with high frequency, which match the present electronic devices with high calculation speed and high throughput. A conventional way to fix this problem is that the high-frequency testing signals are generated by the DUT, and the high-frequency testing signals transmitted to the probe card, and then transmitted back to the DUT to form a loop. it is called a self-testing procedure. The multilayer printed circuit board of the probe card is provided with a feedback element, and the feedback element usually is provided on an outer surface toward the tester of the multilayer printed circuit board. Therefore, the testing signals generated by the DUT have to be transmitted for a long path, which increases the risk of the testing signals being interfered by other elements of the multilayer printed circuit board, and increases the inductance of the circuit. While the frequency of the testing signals is high, the above problem is bigger. It still makes the test imprecise.